Correctly re-combine ALL render passes?
SSS works just like the 3 other "light type" sets do, so you add SSS direct and SSS indirect, multiply the result by SSS color, and sum that result with the other sets.

Shadow is not an image component per-se, since if you rendered your lamps with shadows enabled, they will already be embedded in your lighting passes. (the shadow pass already existed at the time that graphic was created, btw).

So to answer "what is the master routing?", it's just that with the SSS set tacked on the bottom, working the same way.

There are currently no volume passes, so volume shaders cannot be re-assembled in this way. What you can do, however, is use a handful of passes subtractively. For example, let's say you just need to edit glossy indirect to brighten reflections and clear some fireflies, you don't care about any of the other passes.

Rather than render EVERY pass and recombine them all, you can just render the passes you need, subtract the unaltered from the master, edit it, and add it back. For the light passes, you need to do the add+multiply to get the full lighting pass, rather than the split raw passes:


This will work with any shaders, including volumes.